Reactive nitrogen species—nitrous acid (HONO), ammonia (NH3), and amines (NR3)—are present indoors. These reactive nitrogen species are important because of the associated chemical and physical transformations. Outdoors, amines are implicated in particle formation. And HONO is photolabile, which means it decomposes in the presence of light, generating the important oxidant hydroxyl radical. Hydroxyl radicals can then rapidly react with volatile organic compounds, leading to secondary aerosol formation. Detecting concentrations of these chemicals is vital to answering key questions about the chemistry of indoor environments, such as “What is the role of ammonia and amines in indoor chemistry?” and “To what extent do they contribute to new particle formation?” This grant funds a team led by Trevor VandenBoer, Visiting Professor of Chemistry at York University, that aims to develop analytical platforms for the detection of reactive nitrogen indoors. The work plan has three parts. First, the team plans to develop new selective sampling methodologies for the passive collection of HONO, ammonia, and amines in indoor environments. Second, they plan to design and construct a real-time monitor for HONO and total reactive nitrogen that can discriminate between gas and particulate pools. Finally, they will validate the new methods both against traditional benchmarks and through deployment in various indoor environments. The team plans to share their findings through peer-reviewed articles and presentations at several scientific and professional conferences. One postdoctoral fellow, three graduate students, and numerous undergraduates will be trained in the course of the project.